The action of (S)-3-allyl-2-methyl-4-oxocyclopent-2-enyl (1 R)-trans-chrysanthemate, (S)-bioallethrin,on single neurones in the central nervous system of the leech,Hirudo medicinalis

Intracellular recordings from identifiable neurones in the leech segmental ganglion in high (20 mM) magnesium Ringer solution showed that (S)-3-allyl-2-methyl-4-oxocyclopent-2-enyl (1 R)-trans-chrysanthemate, (S)-bioallethrin, induced three phases of activity: (1) hyperexcitability; (2) repeated depolarisations accompanied by trains of action potentials; and (3) block of action potentials. A linear relation between log (time to onset) of both depolarisations and block and the log (applied dose) was observed over the range 3.44 × 10^?7–1.10 × 10^?3M. (S)-Bioallethrin was toxic to leeches at similar concentrations to those effective on isolated ganglia. The possible role of repeated depolarisations in the poisoning process is discussed.